Ribbed cushion bounding walls for ground effect machines



4 y 5 c. s. COCKERELL ETAL 3,

RIBBED CUSHION BOUNDING WALLS FOR GROUND EFFECT MACHINES Filed Dec. 5, 1963 3 Sheets-$heet 1 INVENTOFS C. S. COCKEREILL L.A.HOPK1NS GamWn, W

ATTORNEYS y 1966 c. s. COCKERELL ETAL 3,249,166

RIBBED CUSHION BOUNDING WALLS FOR GROUND EFFECT MACHINES Filed Dec. 5, 1963 a Sheets-Sheet 2 [N VENTORS C. S. COCKERELL L A. HGPKINS mnmm, @ww/Qm A TTORA/ZYS y 1966 c. s. COCKERELL ETAL 3,

RIBBED CUSHION BOUNDING WALLS FOR GROUND EFFECT MACHINES Filed Dec. 5, 1963 3 Sheets-Shem 3 60 FIG.|8. 60

[NVEA/TORS C. '5. COCKERELL LA. HOPKINS m @wn Wow A T TOR/15% United States Patent This invention relates to vehicles for travelling over a surface and which are supported above that surface, at

least in part, by a cushion of pressurised gas formed and contained beneath the vehicle.

In such vehicles it has been proposed to contain the cushion of pressurised gas for at least part of its periphery, and for at least part of the distance between the bottom of the main body of the vehicle and the surface, by one or more downwardly depending flexible walls.

The walls deflect upwards when meeting obstacles such as WBJVBS, rocks, or the like. It is difficult .to provide walls which will deflect sufficiently rapidly and easily to avoid damage to themselves and the transmission of undesirable forces to the main vehicle body and will rapidly return to the normal position after passing over the obstructions. A further difliculty is that it is preferred for one part of the wall to deflect when passing over an obstacle, whilst the remainder of the wall maintains a correct position relative to the surface to avoid undue leakage of pressurised gas from the cushion.

If the. wall comprises a series of separate members, then, although a seal is maintained when travelling over a smooth surface, as soon as an obstacle passes beneath the wall, the individual members deflect by a varying amount, and gas can escape between the members. The

escape of gas can be prevented by making the wall in the form of a continuous member, but it is then extremely diflicult to provide a construction which will allow ready deflection of one part of the wall without causing deflection of a further part. I

According to the present invention, there is provided a vehicle for travelling over a surface and which is supported above that surface, at least in part, by .a cushion of pressurised gas formed beneath the vehicle, the cushion being contained for at least part of its periphery by a wall structure comprising a plurality of deflectable rib members depending downwardly below the lower part of the vehicle and spaced apart to form a series extending for the said part of said periphery of the cushion, the rib members having, collectively, a stiffness in a direction normal to the said periphery suflicient to sustain the pressure of the cushion when formed, cushion-containing means extending between the rib members to assist in containing the cushion while permitting variation in the spaced apart relationship of the rib members, and stabilis ing means attached to each rib member and providing a support tending to return the 'rib members to a datum position.

The rib members can be of rigid material, pivotally attached to the lower part of the vehicle, or can be of a mate-rial which will allow deflection of one part of a member relative to another in a direction parallel to the fore and aft axis of the vehicle, as by bending, or pivoting, but is stiff enough to prevent any substantial sideways deflection due to the cushion pressure. Such stiffness can be obtained by the rib members being in tension, which allows very thin construction to be used.

The deformable stabilising means between the rib members can comprise springs, foamed rubber or plastic or other similar resilient 'means. Alternatively, the de- 3,249,166 Patented May 3, 1966 formable stabilising means can comprise inflated bags or the like, acting as fluid jacks, and conveniently the inflated bag or bags can also serve as the flexible means extending between the rib members and assisting in containing the cushion. As a further alternative, a flexible membrane can extend between the rib members, being acted upon by the cushion pressure and acting both as the deformable stabilising means and the flexible cushioncontaining means.

Although the rib members have a stiffness suflicient to sustain the pressure of the cushion, they can be attached to the lower part of the vehicle in such a manner that they can be moved sideways, for example, either as a whole or by being pivoted about the point of attachment to the lower part of the vehicle, or by bending.

The whole of the distance between the bottom of the main body of the vehicle and the surface can be closed by such rib members. The bottom of each rib member can be provided with surface contact-ing means such as skids or a series of downwardly depending filaments. Alternatively, means may be provided for causing a stream of fluid to'issue from the lower edge of the rib members to assist in containing the cushion and/or in maintaining the bottoms of the mem'bersclear of the surface, and means may also be provided for causing a stream of fluid to issue from the lower edge of the flexible cushioncontaining means to assist in containing the cushion.

The invention will be readily understood by the following description of certain embodiments in conjunction with the accompanying drawings in which:

FIGURES 1 to 5 are fragmentary side views illustratin-g diagrammatically various forms of construction,

FIGURE 6 to 8 illustrate diagrammatically various cross-sections which may be used for the rib members,

FIGURE 9 is an inverted plan View of FIGURE 8,

FIGURES 10 and 11 illustrate further cross-sections for v the rib members,

FIGURE 12 is a diagrammatic side view of a side wall illustrating operation thereof,

FIGURE 13 is a fragmentary side view of a particular embodiment of the invention,

FIGURE 14 is a cross-section on the line AA of FIGURE 13, FIGURE 15 is a cross-section on the line BB of FIGURE 14,

FIGURE. 16 is a similar cross-section to that of FIG- URE 15, illustrating a modification thereof,

FIGURE 17 is a side elevation of a vehicle embodying the invention,

FIGURE 18 is an inverted plan view of the vehicle illustrated in FIGURE 17,

FIGURE 19 is a cross-section on the line C-C of FIGURE 18, and

FIGURE 20 is a cross-section, similar to that of FIG- URE 19, illustrating a modification thereof.

FIGURES 1 to 5 illustrate various forms of construction of the downwardly depending rib members 1, and also indicating variations in the deformable stabilising means positioned between the rib members and in the flexible sealing means extending between the rib members. The rib members 1 extend in a series for at least part of the periphery of a cushion, for example,.along each side of a vehicle, the members being inclined downwardly and rearwardly.

In FIGURES 1 to 3, the rib members 1 are of a material which has sufficient stiffness to resist beingdeflected sideways by the cushion pressure. The members can be of a rigid material, such as wood, but preferably a material having a degree of flexibility is preferred. The members are attached to the lower part of the vehicle by means of flexible members 2 which act as hinges.

tic.

FIGURE 4 illustrates a construction for the rib members 1 which is in the form of an inflated structure constrained to maintain the required shape by cords 3 which extend between the skins 4 of the structure. The skins 4 can be inextensible material or one or other of the skins may be partly or wholly of material which is extensible in a vertical direction. The flexibility of the rib members 1 can be varied by varying the inflation pressure, and, where extensible material is used the profile of the rib members, as seen in FIGURE 4, can also be varied by variation of the inflation pressure. The rib members are inflated by air supplied through a duct 5.

Illustrated in FIGURE 5 is a further form of construction for the rib members 1. In this example each rib member comprises a central web 6, inflated structures 7 and 8 being positioned one on each side of the web. The web 6 is extended at the top of the member, and has an enlarged end 9 which serves to attach -the member to the lower part of-the vehicle. The stiffness of the web may vary, it being formed from material having little or no inherent stiffness, from material which is rigid or from materialwhich is intermediate these two extremes. Considering the total stiffness of the rib member 1, depending upon the inherent stiffness of the web 6, so the stiffness imparted by the inflatable structures 7 and 8 can vary. .In the construction illustrated in FIGURE 5, the inflatable structures are shown permanently inflated, but they can be inflated by air supplied from. a suitable source (not shown) whilst the vehicle is in operation. Further, the total stiffness of the member can be varied by varying the'inflation pressures of the structures 7 and 8. The inflatable structures are constrained by cords 10, or the like, as in FIGURE 4. Preferably the members as a whole have some flexibility and this can be varied by varying the inflation pressure of the structures 7 and 8. Also, by making the skins of the structures 7 and 8 of extensible material, as described in relation to FIGURE 4, the profile of the members can be varied by variation of the relative pressures in the structures.

The deformable stabilising means illustrated in FIG- URE 1 comprise springs 12. The springs are arranged to hold the rib membe-rsl at a predetermined inclination when the vehicle is at its normal operating height when over a smooth surface. This is obtained by maintaining the members at a predetermined spaced apart relationship, i.e. the springs 12 have a predetermined length in the normal position of the members. Springs have a disadvantage in that the load applied by the spring varies with variation in length and to keep the load variation within reasonable limits, long low rate springs are required. The difliculty of using long springs can be eased somewhat by insetting the springs 12 in holes 13 in the member 1. In order to contain the cushion of pressurised gas, a flexible membrane 14 is attached to the inside edges of the members -1, the membrane being curved between each member to provide excess material.

The deformable stabilising means and the flexible sealing means can be combined into a single means. In FIG- URE 2 the spaces between the members 1 are filled with a compressible material 17 such as foamed rubber or plas- The flexibility and resilience of the compressible mater'ial are made appropriate by a suitable choice of material and its dimensions. By making the material 17 impervious to the gas forming the gaseous cushion it will also serve to contain the cushion. Deflection of one or more of the members 1 will result in deformation of the material 17, the resilience of which will provide a load tending to return and maintain the members at the predetermined spaced apart relationship.

An alternative arrangement is illustrated in FIGURE 3, in which an inflatable bag 20 is positioned between the members 1. The bag 20 serves both as a deformable stabilising means which tends to maintain the rib members 1 at the predetermined spaced apart relationship and also as the sealing means to contain the cushion. The

bags 20 can be permanently inflated and sealed but preferably are inflated by air fed through a duct 16. The pressure to which the bags 20 are inflated will determine the load applied to the members, when deflected, which tends to return the members to the normal positions, and also tends to maintain the predetermined spaced apart relationship at normal conditions. The inflated bags 20 thus act as fluid jacks.

Flexible bags 20 are also shown in FIGURES 4 and 5, but foamed material or springs can be used as in FIG- URES l and 2. It is possible to select any combination of the various forms of construction for the rib members 1 and of the various deformable stabilising means and sealing means as is desired. Other forms, not illustrated, can also be used.

The vertical cross-section of the rib" members can vary, depending upon the particular application, some of these variations being illustrated in FIGURES '6 to 10. For a cushion containing means which is positioned at the periphery of a vehicle, the load on the cushion containing means is normally from one side only and is mainly that due to the cushion pressure. The stress in the rib members will vary from top to bottom, being at a maximum at the top and at a minimum at the bottom. The members 1 can therefore taper from top tobottom as illustrated in FIGURE 6. The inner face 23 can be curved, as shown, or straight. It is preferable that the inner surface is the inclined surface as this provides the maximum cushion area. For a containing means such as is positioned between two cushions, then the members 1 can be tapered symmetrically as shown in FIGURE7.

The rib members 1 can also vary in cross-section both when viewed from the side as in FIGURES'l to 5 and also when viewed from the top. Thus the'members can taper to a narrower thickness at the bottom than at the top, or can be curved, or can be thicker or thinner at the centre than at the top and bottom. Also the members can be thicker at the outside edgethan at the inside edge.

Downwardly depending rib members as described above can be usedin combination with fluid curtains. Thus, as illustrated in FIGURE 8, supply ports 25 can be formed in the .bottom of the rib members 1 through which a fluid can be caused to issue. Where the members 1 are inflated, the inflating fluid can be used, or separate fluid supply means can be provided. Where inflatable bags or the like are provided between the rib members 1, as in FIGURES 3, 4 and 5, then as illustrated in FIGURE 9, supply ports 27 can be formed in the bottoms of the bags, the fluid issuing from these ports and from the ports formed in the bottoms of the rib members 1 to form continuous curtains. Where other deformable stabilising means are used, then separate means for forming the intermediate sections of the fluid curtains must be provided. Ifltwo curtains are formed, as in FIGURE 8, then a subsidiary cushion is formed at 26 which tends to maintain a clearanoe between the bottoms of the rib members and the surface over which the vehicle is operating. Alternatively only a single curtain may be formed.

FIGURE 10 illustrates an arrangement in which the rib members, and the intervening deformable stabilising means, are shaped on the inner surfaces 28 in such a manner that a fluid which issues from a supply port 29 will flow down the inner surface, in contact therewith, the fluid flowing between the bottoms of the rib members and the deformable stabilising'means, and the surface. When the clearance between the bottom of a rib member and the surface decreases below normal at least part of the fluid flowing down the inner surface breaks away and forms a subsidiary cushion below the lowerpart of the member which subsidiary cushion assists in deflecting the member upwards. Such an arrangement is described more fully in the specification of copending application Serial No. 322,753, filed November 12, 1963.

When the vehicle is operating over water surfaces, the rib members 1 can be arranged to be at all times partly immersed in the water. To reduce the drag the parts in the water should be as thin as possible although the rib members may be thickened a short distance from the bottom edge to provide the necessary drag to deflect themembers over obstacles. As shown in FIGURE 11, the bottoms of the rib members 1 are quite thin and the intervening deformable stabilising and/or sealing means should similarly be thin. Alternatively the immersed part may comprise aseries of thin plates attached to the bottomof the rib members. When the bottom of the rib members are immersed, they can be conveniently used to propel the vehicle by means of a travelling wave which traverses the wall formed by the members. This can be carried out by shaping the top of the members as shown in FIGURE 11, and providing means 30 for reciprocating the members. Such a propulsion system is described more fully in the specification of co-pending application Serial No. 228,164, filed October 3, 1962, in which there are described other methods of reciprocating the wall which are applicable to the present example.

Over land or water surfaces, flexible skirt members may be attached in the bottoms of the rib members, extending for a part or the whole of the periphery of the cushion. The skirt members can be single thickness of material or can be more complex, for example corrugated.

The operation of the rib members over an obstacle having a smooth curve, such as a wave, is illustrated in FIGURE 12. The downwardly depending rib members are represented by the lines 35, the bottom surface of the main body of the vehicle being shown at 36. As the vehicle passes over the wave, the direction of the vehicle being indicated by the arrow, the rib members move up and down to maintain a seal between the bottom surface 36 of the vehicle and the surface 37. It will be seen that at the bottoms of the wave troughs, the rib members are parallel. As they deflect to move up the advancing face of the wave crest, the rib members are closer together at the bottom than at the top. As the rib members move downwards on the receding face of the wave they are further apart at the bottom than at the top. It is the need to provide for such increase in spacing which requires that the means which closes the gap between the rib members shall in effect have excess material when the rib members are in the normal position. Further, over a smooth surface, the rib members take up a position in which they are parallel to one another but at a steeper angle, as indicated by the dotted lines 38, and this position can be considered as a datum position, from which the rib members deflect up or down. It is therefore necessary to ensure that the flexible means extending between the rib members is capable of allowing the rib members to deflect downwards when over the wave trough, which downward deflection is accompanied by an increase in the distance between the rib members, when measured normal to the plane of the members.

Where the flexible means is combined with the deformable stabilising means, as in FIGURE 2, the variation in the spaced apart relationship is permitted by the stretching and compressing of the material, Whilst where the flexible means is in the form of a membrane as in FIGURE 1 or inflatable bags as in FIGURES 3, 4 and 5,

6 that the ends of the bags are curved at the normal clearance over a smooth surface. This is seen more readily in FIGURES 13, 14 and 15.

The maximum extent to which the rib members 1 will move downwards can be controlled by providing ties between the rib members and the lower part of the vehicle body. Alternatively, or in addition, suitably shaped members can be provided at the front and/0r rear to control this movement. The angle of the rib members can be controlled so that, whether the vehicle is moving forwards or backwards the rib members will deflect towards the back of the vehicle.

The example illustrated in FIGURES 13, 14, and 15 is similar to that illustrated in FIGURE 4 but is to a slightly larger scale and in more detail. FIGURE 13 is a side view of several rib members 40, the deformable stabilising means and the flexible means for containing the cushion being combined in the form of inflatable bags 41. The rib members 40 are in the form of inflated structures constrained to the required cross-section by cords 42, seen more clearly in FIGURE 15. The rib members 40 are attached to the lower part of the vehicle body 43 by hinges 44, and are closed at the top by a rigid or semi-rigid member 45. Air is fed into the rib members from a duct 46 via pipes 47. Air is supplied to the duct 46 via a pipe 48 from a suitable source. It will be appreciated that once the rib members 40 have been inflated there is practically no further flow of air through the pipes 48. The source of air can be a constant pressure source or means may be provided for varying the pressure.

The inflatable bags 41 are open at the top and communicate with a duct 50 which is open at the bottom. Air is fed to the duct 50 via pipes 51 from a suitable source. The pressure of the supply to the duct 50 is lower than that to the duct 46. Both supplies may come from a common source with provision for reducing the pressure of the air supplied to the duct 50 or separate sources may be provided. The supply to the duct 50 may also be at a constant pressure or may be varied, and once the bags are inflated there is only a small flow through the pipes 5 1 to make up for leakages. The gap between the top of the inflated bags and the lower part of the vehicle body is closed by flexible sealing members 52. Part of a sealing member 5 2 and the wall of the duct 50 is omitted in FIGURE 13 to show details more clearly.

The cross-section of the inflated bags 41 can be seen in FIGURE 15. The bags in their full inflated state would be wider than the spacing between the members rib 40, and are positively attached to the rib members, for example, by a suitable adhesive. The bags may be attached for only a narrow region extending from top to bottom of each rib member 40. This provides the maximum flexibility of the bags 41. If the inflation pressure of the bags 41 is greater than the cushion pressure then both ends of the bags are curved so as to be convex on the outer surface, as seen in FIGURE 15. If the inflation pressure is less than the cushion pressure then the wall of each bag adjacent to the cushion will curve inwards as indicated by the dotted line 55 in FIG- URE 15.

The inflatable bags 41 may be divided into separate airtight compartments by diaphragms indicated by the dotted lines 56. The bags may only extend for a part of the Width of the members rib 40. In the simplest form, as illustrated in FIGURE 16, where the cushion pressure is equal to the pressure which is required in the inflated bags, then only the outer part 57 of the bag need be provided, there being no division between the bags and the cushion. This part 57 can be positioned at any desired location across the width of the rib members, but is preferably at the outer edge of the rib members to give the maximum cushion area. A further arrangement is one in which a flexible bag or tube is positioned towards the outer edges of the rib members, a flexible membrane being connected between the inner edges of the rib members.

The lowest position to which the rib members will drop is dependent upon the extensibility of the bag. Downw-ard movement of the rib members, in addition to increasing the distance between members normal to the plane of the members, also imposes a shearing force on the bags. The bags can be so designed that the rib members will be limited in their downward movement and always have a rearwards inclination. This lowest point is usually arranged to coincide with the lowest point in the trough of a wave which is of the maximum height over which the vehicle is intended to operate, or the equivalent for other obstacles.

In order to reduce the possibility of damage and also to reduce wear, surface contacting members 58 can be provided on the bottoms of the rib members 40. These members are particularly desirable for operation over land.

A vehicle embodying the invention is illustrated in FIGURES 17, 18 and 19. Downwardly depending rib members 60 are positioned along each side of the vehicle, being of the form illustrated in FIGURE 6 and as can be seen, can also be provided for the front of the vehicle by suitably staggering the rib members. Combined cushion-containing means and stabilising means in the form of bags, as in FIGURE 3, extend between the rib members. If the space to be contained is also rounded at the rear, cushion containing means according to the invention can also be provided at the rear. In the vehicle illustrated in FIGURES 17, 18 and 19, the cushion is contained at the rear by a member 61 of the form described in the specification of co-pending application Serial No. 322,753, and a similar member 62 is provided across the vehicle at a position intermediate of the ends of the vehicle to subdivide the cushion for providing stability. The cushion is also subdivided in the fore and aft direction by a series of rib members 63, forming a structure according 'to the present invention. Supply ports 64 are formed forward of and adjacent to the members 61 and 62, air issuing from these supply ports and flowing down in contact with the surfaces of the members 61 and 62. Air is fed to the cushion space through ports 70 fed from compressors 7|1.

Where cushion containing means according to the present invention are used in combination with other forms of flexible members, as for example in FIGURES 17, 18 and 19, then it may be necessary to modify the shape of the rib members 60 or the members 6 1 and 62, to provide a satisfactory seal at their junctions. Thus in FIGURE 18 it can be seen that the rib members 60 are modified at the rear to co-operate more satisfactorily with the member 61. Such modifications can be carried out where the rib members 60 co-operate with the member 62 but it is not so necessary. It is also desirable to modify the shape of the rib members at the front of the vehicle to provide an air tight seal where the two sides and the centre division meet.

The rib members 60 and 63 are shown having a shape as illustrated in FIGURES 6 and 7 respectively, and the cross-section of the vehicle is as illustrated in FIGURE 19. By giving the rib members 60 a shape which extends outwards from the cushion as illustrated at 65 in FIGURE 20, an increase in cushion area can be obtained.

Cushion-containing means according to the present invention can be provided for the sides of vehicles, the cushion being contained at front and rear by fluid curtains. If the vehicle is operated at a fast enough speed the curtains can then be shut ofl.

We claim:

1. A vehicle for travelling over a surface and which is supported above that surface, at least in part, by a cushion of pressurised gas formed beneath the vehicle, including a wall structure containing the cushion for at least part of its periphery comprising a plurality of rib members depending downwardly below the lower part of the vehicle and spaced apart in datum positions to form a series extending for the said part of said periphery of the cushion, the rib members being deflectable in directions parallel to said periphery but having, collectively, a stiffness in a direction normal to the said periphery suflicient to prevent deflection in sideways directions and to sustain the pressure of the cushion when formed, cushion-containing means extending between the rib members to assist in containing the cushion while permitting variation in the spaced apart relationship of the rib members, and stabilising means attached to and extending between adjacent rib members and providing a support tending to return the rib members to their datum positions.

2..A vehicle as claimed in claim 1 wherein said rib members are themselves of flexible construction.

3. A vehicle as claimed in claim 2 wherein said'rib members are inflatable.

4. A vehicle as claimed in claim 3 including means for inflating the rib members and for varying the inflation pressure of said rib members.

5. A vehicle as claimed in claim 1 wherein said stabilising means comprises at least one fluid jack positioned between each pair of adjacent rib members.

6. A vehicle as claimed in claim 1 wherein said cushioncontaining means includes said stabilising means.

7. A vehicle as claimed in claim 1 wherein said cushioncontaining means comprises at least one inflatable bag positioned between each pair of adjacent rib members.

3-; A vehicle as claimed in claim 7 including means for inflating said inflatable bags, and means for varying the inflation pressure thereof.

9. A vehicle as claimed in claim ,1 wherein said cushioncontaining means comprises a sheet of flexible material extending between each pair of adjacent rib members.

10. A vehicle as claimed in claim 1 wherein said rib members taper from a larger dimension at the top to a smaller dimension at the bottom.

11. A vehicle as claimed in claim 1 including means for causing a fluid to issue from the lower parts of said cushion-containing means and form a curtain of moving fluid which assists in containing the cushion of pressurised gas.

12.: A vehicle as claimed in claim 11 including means for causing a fluid to issue from the lower par-ts of the rib members and form, with the fluid issuing from the lower parts of the cushion-containing means, a curtain of moving'fluid which assists in containing the cushion of pressurised gas.

13. A vehicle as claimed in claim 12 wherein the rib members and the cushion-containing means are hollow, comprisingmeans for supplying fluid to the interiors of said rib members and cushion-containing means, and ports formed in the bottoms of said rib members and said cushion-containing means from which said fluid issues to form said curtain of moving fluid.

14. A vehicle as claimed in claim 13 wherein said rib members and said cushion-containing means are inflatable, the fluid inflating said rib members and said cushioncontaining means issuing from said ports to form said curtain.

15. A vehicle as claimed in claim 13 wherein said rib members and said cushion-containing means are inflatable, and including separate fluid supply means for supplying fluid to said rib members and said curtain-containing means, respectively.

16; A vehicle as claimed in claim 13 including two horizontally spaced apart parallel ports formedin the bottom surfaces of said rib members and said cushion-containing means, respectively, wherein the fluid issuing from said parallel ports forms parallel curtains of moving fluid forming and maintaining a cushion-of pressurised fluid between said curtains and acting on said bottom surfaces, said cushion tending to maintain a clearance between the surface over which the vehicle is travelling and the bottom surfaces of said rib members and cushion containing References Cited by the Examiner means.

17. A vehicle as claimed in claim 1 including surface UNITED STATES PATENTS contacting members on the lower parts of the rib mem- 3,066,753 12/1962 Hurley et 180 7 bers. 5-

18. A vehicle as claimed in claim 1 wherein the wall FOREIGN PATENTS structure extends for whole periphery of the bottom of the 1,23 8,499 7/1960 Francevehicle to define a cushion space. 113391354 8/1963 France 19. A vehicle as claimed in claim 18 including means I extending across the bottom of the vehicle to subdivide 10 BENJAMIN HERSH Pnmmy Exammer' the said cushion space. M. S. SALES, Assistant Examiner. 

1. A VEHICLE FOR TRAVELLING OVER A SURFACE AND WHICH IS SUPPORTED ABOVE THAT SURFACE, AT LEAST IN PART, BY A CUSHION OF PRESSURISED GAS FORMED BENEATH THE VEHICLE, INCLUDING A WALL STRUCTURE CONTAINING THE CUSHION FOR AT LEAST PART OF ITS PERIPHERY COMPRISING A PLURALITY OF RIB MEMBERS DEPENDING DOWNWARDLY BELOW THE LOWER PART OF THE VEHICLE AND SPACED APART IN DATUM POSITIONS TO FORM A SERIES EXTENDING FOR THE SAID PART OF SAID PERIPHERY OF THE CUSHION, THE RIB MEMBERS BEING DEFLECTABLE IN DIRECTIONS PARALLEL TO SAID PERIPHERY BUT HAVING, COLLECTIVELY, A STIFFNESS IN A DIRECTION NORMAL TO THE SAID PERIPHERY SUFFICIENT TO PREVENT DEFLECTION IN SIDEWAYS DIRECTIONS AND TO SUSTAIN THE PRESSURE OF THE CUSHION WHEN FORMED, CUSHION-CONTAINING MEANS EXTENDING BETWEEN THE RIB MEMBERS TO ASSIST IN CONTAINING THE CUSHION WHILE PERMITTING VARIATION IN THE SPACED APART RELATIONSHIP OF THE RIB MEMBERS, AND STABILISING MEANS ATTACHED TO AND EXTENDING BETWEEN ADJACENT RIB MEMBERS AND PROVIDING A SUPPORT TENDING TO RETURN THE RIB MEMBERS TO THEIR DATUM POSITIONS. 